This application generally relates to a vehicle clutch assembly and associated engine control system that more precisely controls vehicle speed during low-speed vehicle operations. More particularly, this invention relates to an engine control system that indirectly effects clutch slippage for a centrifugal clutch assembly in response to selection of a dedicated maneuvering mode for low-speed vehicle operation.
Ideally, transmissions include a deep reduction or low-speed creep ratio that allows the vehicle to operate at very low-speeds. This deep reduction is not utilized during a significant portion of the overall operating time of the vehicle. Thus, the inclusion of structure within the transmission to provide the deep reduction significantly increases the cost of the transmission.
One solution has eliminated this deep reduction from the transmission by providing for a simulated creep ratio. In this creep control mode, a wide range of accelerator pedal movements result in a narrowed band of clutch and engine control. While this solution has been effective for automated plate type clutches, there is a similar need for improved clutch control in transmissions equipped with a centrifugal clutch.
A centrifugal clutch typically includes a rotating input component that is driven by a vehicle power source, such as an electric motor or engine. The rotating input component further includes weighted elements mounted for rotation with the input component, which move radially outwardly during rotation as a result of centrifugal forces. As the weighted elements move outwardly in a radial direction, the input member frictionally engages a driven output component coupled to a transmission. A clamping component clamps or holds the engaged friction surfaces of the input and output components together at a minimum clamp force to permit torque to be transferred from the power source to the transmission via the clutch assembly.
There is a need for a maneuvering mode capability with configurations that use a centrifugal clutch assembly that will improve speed control at low-speed vehicle operations without the added expense of deep reduction gears.